But that doesn't make any sense. If the scenes had played out without the plot contrivance of willfully keeping characters in the dark, then Rick & Co would have grilled Michonne relentlessly to find out EVERYTHING she knew, before they attempted a rescue.
This is coming off the loss of two of their people due to allowing outsiders into their lives. This random lady could easily have been one of the kidnappers. How were they to know whether they could trust her? They would have demanded to know everything, like especially WHO took Glenn and Maggie? What did he look like? How did it happen? Oh what? They seemed like they knew each other? He has a brother? He only has one hand?!
Plus, she can keep her guard up will still using the power of speech.
It seems to me that the portrayal and writing for the character of Michonne seems to be "silent but deadly" but it's not working. It's aggravating. And does not make for a compelling character. I do hope she evolves into a more dimensional character because I really need some more females on this show to root for.